While that severealy limited which networks you could use the unlocked iPhone 4 with, the price of purchasing one was probably enough to put most people off anyway. The 16GB unlocked iPhone costs $649, where as the 32GB is $749.

Even with the extrotionate pricing it seems unlocked iPhones are proving popular and T-Mobile already counts over one million users on its network. Apple may even be struggling with demand as it is expected to introduce a new system next week that allows an AT&T iPhone 4 to be unlocked at the register.

What that means is all AT&T iPhone 4 stock Apple has can also be treated as unlocked iPhone 4 stock.

The switch to this system should mean Apple has no more problems meeting demand for either AT&T or unlocked handsets. All it has to do is order both kinds and switch when necessary. The one remaining question is what happens if they run out of AT&T handsets, can they swicth an unlocked one over in the same way?

If the expectation of an iPhone 4S appearing alongside an iPhone 5 in September also turns out to be true, we have to wonder if Apple will carry on this practice at its retail locations. Will you be able to purchase a 4S unlocked from day one? Or will we be subjected to lock-in deals again with AT&T?